Hall current sensor based on tunnel magnetoresistance composite correction

Abstract

The application provides a Hall current sensor based on tunnel magnetoresistance composite correction, which comprises a ring-shaped support structure for sleeving around a conductor with a circular cross section to be measured; a TMR sensor mounted on the ring-shaped support structure and symmetrically distributed around the conductor; a current Hall sensor located in an adjacent plane; the TMR sensor comprises a high magnetic permeability magnetic shunt and a tunnel magnetoresistance TMR; a differential detection circuit for differentially processing output signals of the TMR sensors located in symmetric positions; and a data processing unit electrically connected with the TMR sensor and the current Hall sensor. The application adopts the adjacent plane arrangement of the tunnel magnetoresistance and the Hall sensor, captures current transient changes by using the inertial delay characteristics of the adjacent plane tunnel magnetoresistance under the premise of not affecting the sampling of the Hall sensor, detects weak magnetic field changes, and provides a phase correction time reference for the inherent phase delay of the Hall sensor.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of current detection sensors, in particular to a Hall current sensor based on tunnel magnetoresistance composite correction. BACKGROUND

[0002] The power closed-loop control of a nuclear fusion device (such as a tokamak) is the key to controlling the plasma balance and shape, and has extremely high requirements for current sampling accuracy and low phase delay in a strong magnetic field and large current operating environment; in a strong magnetic field and large current environment, the Hall current sensor is always the mainstream choice for nuclear fusion device power current measurement due to its electrical isolation, wide range and anti-interference performance, and progressive degradation characteristics, and can be reliably guaranteed; the working principle of the current Hall element is that the deflection of the carrier under the action of the Lorentz force generates a voltage, and the migration speed of the carrier in the semiconductor material has an upper limit, so there is a physical delay, which is easy to form a vicious cycle of "delay-bias amplification" in the power closed-loop control. In a strong magnetic field environment, the installation position deviation of the current Hall element will cause the linearity of the Hall output to deteriorate. The Hall element will change due to radiation, causing sensitivity drift, which poses a challenge to the long-term stable operation of the power system.

[0003] The physical essence of tunnel magnetoresistance TMR is an electron tunneling process, and the extremely low inertial delay characteristic (time scale is femtosecond level) enables TMR to accurately capture transient changes in current. The TMR sensitivity is 100-1000 times that of the Hall element, and the signal-to-noise ratio is greater than or equal to 60dB in a weak magnetic field, so that TMR can more accurately capture and detect weak magnetic field changes in real time than Hall elements; TMR can achieve differential measurement through a ring-shaped symmetric layout, and the current conductor should be coincident with the magnetic ring axis, when the installation position deviates from the center, the magnetic field change amount of the symmetric element is equal in size and opposite in direction, and the differential output can offset the deviation influence, thereby providing a magnetic field reference for the current Hall, which makes up for the strict requirement of Hall sampling on installation accuracy; the TMR zero magnetic field output drift (less than or equal to 1mV / ℃) and hysteresis (less than or equal to 0.1%) are better than those of the Hall, which can provide a stable calibration reference for the Hall and suppress the accuracy drift in long-term use; in nuclear fusion engineering, the current detection device needs to meet the degradation operation requirement after a single-point failure of current detection, and TMR may cause the breakdown of the magnetic tunnel junction barrier layer under extreme conditions, resulting in irreversible damage, which is difficult to meet the reliability requirement and cannot be used as the main current detection device independently. Therefore, in view of the deficiencies of the prior art, it is necessary to provide a Hall current sensor based on tunnel magnetoresistance composite correction to overcome the deficiencies of the prior art, which meets the safety specification requirements of nuclear fusion device power current detection and improves the current detection performance. SUMMARY

[0004] The application aims to avoid the shortcomings of the prior art and provide a Hall current sensor based on tunnel magnetoresistance composite correction suitable for the safety and control requirements of a nuclear fusion device power supply, aiming to develop existing tunnel magnetoresistance TMR and magnetic shunt technology, apply tunnel magnetoresistance in a strong magnetic field environment (attenuated to the linear region), and further reduce the output linearity deterioration caused by the installation deviation of the current Hall, thereby improving the measurement accuracy; reduce the large current measurement phase delay caused by the Hall effect itself, and improve the dynamic control performance of the fusion power supply system. The specific technical scheme is as follows:

[0005] A Hall current sensor based on tunnel magnetoresistance composite correction, comprising:

[0006] A ring-shaped support structure for sleeving around a circular cross-section conductor to be measured;

[0007] A plurality of TMR sensors mounted on the ring-shaped support structure and symmetrically distributed around the conductor;

[0008] At least one current Hall sensor is located in the adjacent plane;

[0009] The TMR sensor comprises a high magnetic permeability magnetic shunt and a tunnel magnetoresistance TMR, and the high magnetic permeability magnetic shunt is adjacent to the tunnel magnetoresistance TMR;

[0010] A differential detection circuit for differentially processing the output signals of the TMR sensors located in the symmetric positions to obtain a differential output signal;

[0011] And a data processing unit electrically connected with the TMR sensor and the current Hall sensor.

[0012] The application has the following beneficial effects:

[0013] High precision and low phase delay control of the current of the nuclear fusion device (such as a tokamak) power supply is the key to accurately control the plasma balance and shape, and the detection of the current is a prerequisite for the current control. In a strong magnetic field and large current environment, the Hall current sensor has the advantages of electrical isolation, wide range and anti-interference, and has a gradual degradation characteristic (the performance slowly, continuously and predictably decreases over time), and is always a reliable choice for current measurement of the nuclear fusion device power supply. However, the Hall sensor has inherent physical delay due to the migration speed limitation of the carrier in the semiconductor, which will lead to a vicious cycle of "delay-deviation amplification" in the power supply closed-loop control, which is a performance shortcoming of the Hall sensor. However, such as the Rogowski coil current sensor and the magnetic optical current sensor, it is difficult to cope with the complex working conditions of the nuclear fusion device and ensure the safety and reliability of the system. Therefore, even though the Hall sensor has performance shortcomings in measurement, it is still the mainstream choice for current measurement of the nuclear fusion device power supply system.

[0014] The Hall current sensor based on the tunnel magnetoresistance composite correction in the application can significantly reduce the influence of the Hall sensor sampling phase delay, reduce the magnetic field deviation caused by the position deviation in the Hall installation process, greatly improve the use performance of the Hall sensor, and improve the precision of the nuclear fusion device power control.

[0015] The innovation adopts the adjacent plane arrangement of the tunnel magnetoresistance and the Hall sensor, and the composite layout structure. Without affecting the Hall sensor sampling, the adjacent plane tunnel magnetoresistance with extremely low inertial delay characteristics (femtosecond level) is used to accurately capture the current transient change and detect weak magnetic field change, so as to provide a phase correction time reference for the inherent phase delay of the Hall sensor.

[0016] Since the tunnel magnetoresistance itself cannot meet the requirements of the single-point failure degradation operation of the nuclear fusion engineering current detection, the innovation uses the sensitivity coefficient of the tunnel magnetoresistance compared with the current Hall to design a magnetic shunt, attenuates the strong magnetic field according to a specific proportion, and ensures that the tunnel magnetoresistance sensitive element works in the linear interval.

[0017] In a strong magnetic field environment, the installation position deviation of the large current Hall element will cause the deterioration of the linearity of the Hall output, the innovation adopts the differential measurement of the tunnel magnetoresistance ring structure and the cross-symmetric layout, the size of the magnetic field change detected by the symmetrical tunnel magnetoresistance is equal, and the direction is opposite, the differential output offsets the deviation influence, and then provides installation deviation compensation for the Hall detection and improves the detection precision. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is the structure design and signal processing flowchart of the application;

[0019] Figure 2 is the TMR differential output circuit diagram. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical scheme and advantages of the application clearer, the application is further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the application, and are not used to limit the application. In addition, the technical features involved in each embodiment of the application described below can be combined with each other as long as they do not conflict with each other. In order to achieve the above purpose, the application adopts the following technical scheme.

[0021] As Figure 1As shown, this invention provides a Hall current sensor based on tunnel magnetoresistive composite correction, comprising: a ring support structure for mounting around a conductor with a circular cross-section to be measured; multiple TMR sensors mounted on the ring support structure and symmetrically distributed around the conductor, preferably four in a cross-shaped symmetrical arrangement; at least one current Hall sensor located in an adjacent plane; the TMR sensor includes a high permeability magnetic shunt and a tunnel magnetoresistive TMR, the high permeability magnetic shunt being adjacent to the tunnel magnetoresistive TMR and used to guide most of the magnetic field generated by the conductor to flow along the high permeability magnetic shunt, allowing only a portion of the magnetic field to act on the tunnel magnetoresistive TMR, thereby weakening the magnetic field strength flowing through the tunnel magnetoresistive TMR and preventing magnetic saturation of the tunnel magnetoresistive TMR; a differential detection circuit for differentially processing the output signal of the TMR sensor located in symmetrical positions to obtain a differential signal that reflects the magnetic field of the measured current and suppresses common-mode interference; and a data processing unit electrically connected to the TMR sensor and the current Hall sensor.

[0022] The high-permeability magnetic shunt is made of a soft magnetic material with high permeability and moderate saturation flux density. It is arranged close to and parallel to the tunnel magnetoresistive (TMR), and its shape is adapted to the cross-section of the TMR. It is in contact with the magnetic core of the magnetic ring. When the magnetic field generated by the conductor current enters the high-permeability magnetic shunt, most of the magnetic field forms a closed magnetic circuit along the high-permeability magnetic shunt, and a small part of the magnetic field forms a closed magnetic circuit along the tunnel magnetoresistive (TMR). This limits the magnetic field strength of the tunnel magnetoresistive (TMR) to its linear operating range.

[0023] The differential detection circuit subtracts the outputs of a pair of symmetrically arranged TMR sensors in the vertical direction to obtain a first differential signal; and subtracts the outputs of a pair of symmetrically arranged TMR sensors in the horizontal direction to obtain a second differential signal. The first differential signal and the second differential signal are used together to calculate the magnetic field generated by the measured current and the conductor eccentricity deviation. The common-mode interference magnetic field is canceled in the differential operation, while the magnetic field signal of the measured current is enhanced in the differential result.

[0024] like Figure 1 As shown, the ring-shaped support structure uses a permanent magnet ring to construct a closed magnetic field loop, confining the magnetic field generated by the conductor current within the core of the permanent magnet ring to prevent magnetic field leakage. The radius of the magnetic field is determined accordingly. Below, the Hall element detects a magnetic field proportional to the current; the Hall element is located in the air gap of the magnetic core, and the subsequent stage is connected to the output sampling circuit. The magnetic field strength B within the magnetic ring is formed by the conduction current; the radius of the magnetic field is... .

[0025] The tunnel magnetoresistance TMR is located on the plane of the permanent magnet magnetic ring perpendicular to the wire, the axis of the permanent magnet magnetic ring coincides with the wire, the tunnel magnetoresistance TMR1-4 is arranged, and there are four in total, which are located at the upper and lower vertices of the left and right ends of the permanent magnet magnetic ring, that is, a cross symmetric arrangement.

[0026] The high permeability magnetic shunt is located on both sides of the tunnel magnetoresistance TMR, is placed in parallel, and the top end is connected with the magnetic core of the permanent magnet magnetic ring, and the high permeability characteristic is used to absorb the magnetic field and separate the magnetic field from the tunnel magnetoresistance TMR, and the whole is embedded in a ferrite substrate to form a closed magnetic circuit.

[0027] The high permeability magnetic shunt adopts a permalloy magnetic bridge for magnetic separation, and the permalloy magnetic bridge is located on both sides of the tunnel magnetoresistance TMR. According to the magnetic Ohm law, the magnetic flux flowing through the permalloy magnetic bridge and the tunnel magnetoresistance TMR is inversely proportional to the respective magnetic resistance, so by selecting a low-resistance permalloy magnetic bridge to shunt the magnetic field in the permanent magnet magnetic ring, the strong magnetic field is attenuated by a certain proportion and flows through the tunnel magnetoresistance TMR, and then the tunnel magnetoresistance TMR works in a strong magnetic field environment and performs linear output. In the magnetic separation design, in order to improve the measurement accuracy, the tunnel magnetoresistance model is selected as Crocus CT100, which has a linear error of less than 0.5% in the range of ±20mT, and the magnetic separation ratio of the tunnel magnetoresistance TMR and the permalloy magnetic bridge is set to 1:99.

[0028] According to the magnetic Ohm law: , is the magnetic motive force, is the magnetic resistance, is the magnetic flux, and the magnetic motive forces of the parallel branches are equal , is the magnetic motive force of the high permeability magnetic shunt permalloy magnetic bridge, is the magnetic motive force of the tunnel magnetoresistance TMR, so , is the magnetic flux of the high permeability magnetic shunt permalloy magnetic bridge, is the magnetic flux of the tunnel magnetoresistance TMR, is the magnetic resistance of the high permeability magnetic shunt permalloy magnetic bridge, is the magnetic resistance of the tunnel magnetoresistance TMR, and the magnetic resistance calculation formula is , wherein is the length of the magnetic circuit, is the magnetic permeability, is the cross-sectional area, the magnetic separation ratio of the tunnel magnetoresistance TMR and the permalloy magnetic bridge is set to 1:99, and , is the length of the magnetic circuit of the tunnel magnetoresistance TMR, is the magnetic permeability of the tunnel magnetoresistance TMR, is the cross-sectional area of the tunnel magnetoresistance TMR, is the length of the magnetic circuit of the permalloy magnetic bridge, is the permeability of the permalloy magnetic bridge, is the cross-sectional area of the permalloy magnetic bridge; the magnetic bridge is selected to be permalloy (Ni-Fe alloy 1J85), , TMR is matched with ceramic substrate, ; according to the relationship between magnetic flux and magnetic field , the magnetic field is shunted to the tunnel magnetoresistance TMR: , is the magnetic field at the tunnel magnetoresistance TMR, is the total magnetic field in the magnetic ring of the permanent magnet, designed (corresponding to the maximum current 100kA), T represents Tesla (Tesla), which is the unit of magnetic induction, has , meets the linear operating range of Crocus CT100 (±20mT), and has no risk of saturation.

[0029] As shown in Figure 2 , the differential output circuit uses a symmetrically matched TMR sensor to output, suppresses the synchronous variation caused by temperature, installation deviation, etc., extracts the differential mode signal to react to the magnetic field variation; the TMR sensor adopts an open-loop structure to directly output the resistance signal, reduces the reaction delay, avoids loop high-frequency oscillation, and reduces system power consumption; TMR1 and TMR3 are vertically symmetrical, and their output voltages are respectively 、 , TMR2 and TMR4 are horizontally symmetrical, and their output voltages are respectively 、 , in the circuit 、 , 、 、 、 are sampling resistors, and the differential output satisfies: ; the differential output satisfies: ; the tunnel magnetoresistance TMR characteristics are consistent, that is , is the zero magnetic field output, is the tunnel magnetoresistance TMR sensitivity, is the magnetic field, 、 、 、 are the magnetic fields of tunnel magnetoresistance TMR1, TMR2, TMR3, and TMR4, respectively, when there is common-mode interference (such as temperature causing synchronous drift ), there are: , , , Vertical tunnel magnetoresistive differential output That is, the common-mode interference ΔV0 is canceled out, and only the magnetic field differential-mode signal is retained. Horizontal tunnel magnetoresistive differential output That is, the common-mode interference ΔV0 is canceled out, and only the magnetic field differential-mode signal is retained. .

[0030] Take the distance between the tunnel magnetoresistance and the center of the conductor The conductor's center shifted due to installation misalignment. This makes the distance from the center of the conductor... The tunnel magnetoresistive magnetic field is The magnetic field at the symmetrical tunnel magnetoresistance is Reverse equal change The distance between the tunnel magnetoresistance and the center of the conductor Magnetic field at time The difference in magnetic field introduced by the installation position deviation.

[0031] There is a magnetic field difference when the current Hall effect is installed with a deviation compared to when there is no installation deviation. (During Hall installation deviation, the axis of the current conductor under test, the current Hall, and the magnetic ring containing the tunnel magnetoresistor do not coincide.) The tunnel magnetoresistor (TMR) and the Hall are installed on adjacent planes and are coaxial, with the same magnetic ring radius. The difference in the magnetic field of the tunnel magnetoresistor is... Difference between current and Hall magnetic field Proportional, with , ( (The spatial coupling coefficient, calibrated experimentally), when the conductor and the magnetic ring axis are not coincident, the tunnel magnetoresistive output voltage difference is [value missing]. The difference between the current and the Hall magnetic field was obtained. , For tunnel magnetoresistive (TMR) sensitivity; the actual Hall output needs to eliminate the influence of the bias magnetic field, and the corrected Hall output amplitude is as follows: , This is the actual output voltage of the Hall effect sensor. To adjust the Hall output amplitude for Hall sensitivity.

[0032] TMR is based on the tunneling magnetoresistance effect. Since electron tunneling is inertial, the tunneling magnetoresistance response can be considered an ideal, time-delay-free reference. It is calculated separately using signal processing circuits. and And calculate the phase difference value. This is the output voltage of the tunnel magnetoresistive (TMR) system. The output voltage of the Hall element is [value], and the phase difference between the two is [value]. Based on the relationship between the phase difference and time delay of a sinusoidal signal: Therefore: , is the angular frequency of the current signal, is the Hall time constant, the output time-domain correction model considering the current Hall time constant is: , the Hall theoretical output value is obtained by phase and amplitude correction: .

Claims

1. A Hall current sensor based on tunnel magnetoresistance composite correction, characterized in that, Comprising: a ring-shaped support structure for fitting around a round cross-section conductor to be measured; a plurality of TMR sensors mounted on the ring-shaped support structure and symmetrically distributed around the conductor; at least one current Hall sensor located in an adjacent plane; the TMR sensor comprises a high permeability magnetic shunt and a tunnel magnetoresistance (TMR), the high permeability magnetic shunt being adjacent to the tunnel magnetoresistance (TMR); a differential detection circuit for differentially processing the output signals of the TMR sensors located in symmetric positions to obtain a differential output signal; and a data processing unit electrically connected to the differential detection circuit for signal processing.

2. The Hall current sensor based on tunnel magnetoresistance composite correction according to claim 1, characterized in that, Comprising: the high permeability magnetic shunt is made of soft magnetic material with high permeability and moderate saturation magnetic flux density, is arranged close to and parallel to the tunnel magnetoresistance (TMR), and has a shape adapted to the cross section of the tunnel magnetoresistance (TMR) and is in contact with the magnetic core of the magnetic ring.

3. The Hall current sensor based on tunnel magnetoresistance composite correction according to claim 1, characterized in that, Comprising: the plurality of TMR sensors is preferably four and arranged in cross symmetry.

4. The Hall current sensor based on tunnel magnetoresistance composite correction according to claim 1, characterized in that, Comprising: the ring-shaped support structure adopts a permanent magnet magnetic ring.

5. The Hall current sensor based on tunnel magnetoresistance composite correction according to claim 4, characterized in that, Comprising: the high permeability magnetic shunt is located on both sides of the tunnel magnetoresistance (TMR), is placed in parallel and has a top end in contact with the magnetic core of the permanent magnet magnetic ring, the high permeability magnetic shunt and the tunnel magnetoresistance (TMR) perform magnetic shunting, and the whole is embedded in a ferrite substrate to form a closed magnetic circuit.

6. The Hall current sensor based on tunnel magnetoresistance composite correction according to claim 1, characterized in that, Comprising: the high permeability magnetic shunt adopts a permalloy magnetic bridge.

7. The Hall current sensor based on tunnel magnetoresistance composite correction according to claim 1, characterized in that, Comprising: the tunnel magnetoresistance (TMR) is of the type Crocus CT100, which has a linear error of <0.5% in the range of ±20mT, and the magnetic shunting ratio is set to 100:

1.

8. The Hall current sensor based on tunnel magnetoresistance composite correction according to claim 1, characterized in that, Comprising: The differential detection circuit subtracts the outputs of a pair of symmetrically arranged TMR sensors TMR1, TMR3 in the vertical direction to obtain a first differential signal ; and subtracts the outputs of a pair of symmetrically arranged TMR sensors TMR2, TMR4 in the horizontal direction to obtain a second differential signal , and the first differential signal and the second differential signal are used to calculate the magnetic field generated by the measured current and the deviation of the eccentric position of the conductor.

9. The Hall current sensor based on tunnel magnetoresistance composite correction according to claim 1, characterized in that, Vertical direction differential output signal wherein, is a tunnel magnetoresistance, TMR, sensitivity, , are tunnel magnetoresistance, TMR1, TMR3, magnetic fields, respectively; horizontal direction differential output signal , , are tunnel magnetoresistance, TMR2, TMR4, magnetic fields, respectively, and the tunnel magnetoresistance differential output caused by mounting offset is calculated by the vector sum of horizontal and vertical direction double differential .

10. The Hall current sensor based on tunnel magnetoresistance composite correction according to claim 9, characterized in that, the current Hall sensor outputs after time delay correction are: ； wherein, is the actual output value of the Hall, is the Hall sensitivity, is the tunnel magnetoresistance, TMR, sensitivity, is the Hall lag time, is the tunnel magnetoresistance differential output, is the spatial coupling coefficient.

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